In patients with AIDS and other immunosuppressive disorders, both the high incidence of Pneumocystis carinii pneumonia and the increasing numbers of patients at risk have necessitated the development of diagnostic techniques which are less invasive than bronchoscopy or open lung biopsy. This project has involved prospective assessment of the sensitivity of induced sputum in diagnosing P. carinii in immunosuppressed adults, including patients with AIDS. Specimens are obtained, using hypertonic saline nebulization, by Critical Care Therapists in CCMD and processed in the microbiology lab of CP/CC. Both toluidine blue staining and monoclonal antibody immunofluorescent techniques are used to determine the presence of cysts in the sputum. Patients with a "positive" sputum receive therapy based on that result, and those with a "negative" sputum undergo bronchoscopy to determine if P. carinii was missed by the sputum technique. Sensitivity is greater than 90% at the present time. Data from our group have appeared in The New England Journal of Medicine and Annals of Internal Medicine which indicate the effectiveness and safety of this technique as an alternative to bronchoscopy to diagnose P. carinii.